The present invention relates to a vehicle tire comprising a tread in which tread grooves are molded.
The profiling of vehicle tires serves to ensure the adhesion of that tire also with a non-dry and non-solid surface. With a wet road, the water must be led away through the tread grooves of the vehicle tire in order to ensure the contact to the road. Despite this, it has not been possible up to the present day to prevent a situation in which the vehicle tire starts to swim or float on the water present on the road above a certain vehicle speed and so-called aquaplaning arises.
The invention is based on the object of improving a vehicle tire of the initially named kind in this respect. In particular the leading away of water should be improved and a floating of the vehicle tire even at higher speeds is to be avoided.
This object is satisfied in that the tread grooves are curved in such a way that during the rolling of the tire, they always open at least substantially perpendicularly into the front boundary line of the tire contact patch.
Through this design the path which a water particle has to traverse in order to move out of the tire contact patch is reduced to a minimum. Through the short path not only is the time for the leading away of the water particles minimized, but rather the water particles are also transported relatively far from the tire contact patch, whereby the leading away of water is particularly effective. At the same time the tread grooves of the invention result in the sound emission being minimized. Since the tread grooves of the invention open substantially perpendicularly into the front boundary line of the tire contact patch, a simultaneous striking action of a longer tread edge on running into the tire contact patch does not arise, whereby a minimum noise emission is achieved.
The front boundary line of the tire contact patch is in this arrangement defined as that line which is characterized in that all rubber particles which lie on this line simultaneously contact the road surface during rolling of the tire. Extremely unfavorable with respect to the noise emission would be a tread groove which extends parallel to the front boundary line, because in this case the edges of the tread simultaneously strike the road surface. This is avoided by the tread design of the invention.
In accordance with a further aspect of the invention, the opening angle of the curved tread grooves which angle is substantially 90xc2x0 is related to the shape of the contact patch in a particular state of travel, in particular at a speed of travel when there is danger of aquaplaning. It is known that the shape of the tread contact patch changes with increasing vehicle speed. On the other hand, it is known that the danger of aquaplaning starts approximately at a speed of 80 to 100 km/h. By the matching of the tread design to the shape of the tire contact patch at a higher vehicle speed, a situation is achieved in which the leading away of water is ideal, in particular in a critical driving condition, in that a perpendicular opening of the curved tread grooves into the front boundary line of the tire contact patch is present with the then given shape of the tire contact patch.
In accordance with a further aspect of the invention the curved tread grooves end axially inwardly at a distance from the center of the tread. In particular the curved tread grooves end axially inwardly in a tread rib or tread groove extending around the tire in the circumferential direction. In this way a stable tread design is achieved.
In accordance with a further aspect of the invention a tread groove extending in the circumferential direction is provided at the center of the tread. Perpendicular opening into the boundary line of the tire contact patch signifies an orientation in the circumferential direction of the tire at the center of the tread. A corresponding encircling or circumferentially extending groove at the center of the tread is thus particularly suited for the leading away of water.
In accordance with a further aspect of the invention at least one further tread groove extending around the tire in the circumferential direction is provided, which preferably crosses the curved tread grooves. These further tread grooves lead to an improved structuring of the tread pattern.
In accordance with a further aspect of the invention additional further tread grooves are additionally provided, in particular tread grooves extending transversely to the curved tread grooves. Two adjacent tread grooves are in each case preferably connected to one another via at least one transverse groove. These designs also serve for improved structuring of the tread pattern.